Project description:RNA-sequencing has been used to obtain and observe transcriptome-wide differences that occur in two parasspeckle-deficient, MYCN-amplified/model high-risk and one paraspeckle-abundant, non-MYCN-amplified/low-risk cell lines, to decipher the role of paraspeckles in this cancer type.
Project description:MYCN amplification in neuroblastoma leads to aberrant expression of MYCN oncoprotein, which binds active genes promoting transcriptional amplification. Yet how MYCN coordinates transcription elongation to meet productive transcriptional amplification and which elongation machinery represents MYCN-driven vulnerability remain to be identified. We conducted a targeted screen of transcription elongation factors and identified the super elongation complex (SEC) as a unique vulnerability in MYCN-amplified neuroblastomas. MYCN directly binds EAF1 and recruits SEC to enhance processive transcription elongation. Depletion of EAF1 or AFF1/AFF4, another core subunit of SEC, leads to a global reduction in transcription elongation and elicits selective apoptosis of MYCN-amplified neuroblastoma cells. A combination screen reveals SEC inhibition synergistically potentiates the therapeutic efficacies of FDA-approved BCL2 antagonist ABT-199, in part due to suppression of MCL1 expression, both in MYCN-amplified neuroblastoma cells and in patient-derived xenografts. These findings identify disruption of the MYCN-SEC regulatory axis as a promising therapeutic strategy in neuroblastoma.
Project description:The MYCN locus is amplified in about half of high-risk neuroblastoma tumors. To identify genomic loci occupied by MYCN protein in the MYCN-amplified neuroblastoma cell lines NGP, Kelly and NB-1643, we performed chromatin immunoprecipitation coupled with Next-Generation Sequencing (ChIP-seq) using an anti-MYCN antibody.
Project description:Purpose: Identify new targets in MYCN-amplified Neuroblastoma Methods: ChIP-Seq experiments were performed on Kelly and LAN-1 neuroblastoma cells by using the following antibodies: anti-EZH2 (Cell Signaling 5246S); anti-H3K27me3 (Millipore 07-449); anti-H3K4me3 (Abcam ab8580). We evaluated the global EZH2 PRC2-dependence by identifiying direct genome-wide target genes for EZH2, H3K27me3 and H3K4me3. Results: We found that EZH2 serves a PRC2-dependent function in neuroblastoma, repressing neuronal differentiation. Moreover, EZH2-regulated genes were strongly repressed in MYCN-amplified and high-risk primary tumors. Conclusion: Our study supports testing EZH2 inhibitors in patients with MYCN-amplified neuroblastoma.
Project description:Purpose: Identify new targets in MYCN-amplified Neuroblastoma Methods: Kelly and LAN-1 neuroblastoma cells were treated in duplicate with 2 uM GSK126 (Excess Biosciences M60071-2) or DMSO for 2 or 5 days. RNA was extracted from cells with the RNeasy Kit (Qiagen). RNA libraries were prepared for sequencing using standard Illumina protocols. The pool of sixteen samples was sequenced on two lanes of an Illumina HiSeq, generating single end reads of 32-76 bp length. Transcript abundance (reads and FPKM scores) at GRCh37/hg19 RefSeq gene level was computed with the Feature Counts method implemented in the Bioconductor v3.2 Rsubread package (Liao et al., 2014). Results: Pharmacological suppression of EZH2 inhibited neuroblastoma growth. Transcriptomic analysis revealed that EZH2 serves a PRC2-dependent function in neuroblastoma, repressing neural differentiation. Moreover, EZH2-regulated genes were strongly repressed in MYCN-amplified and high risk primary tumors. These observations demonstrate that MYCN upregulates EZH2 leading to inactivation of a tumor suppressor program in neuroblastoma. Conclusion: Our study supports testing EZH2 inhibitors in patients with MYCN-amplified neuroblastoma.
Project description:Here we sought metabolic alterations specifically associated with amplified MYCN as nodes to indirectly target the MYCN oncogene. Liquid chromatography-mass spectrometry-based proteomics identified 7 proteins consistently correlated with MYCN in proteomes from 49 neuroblastoma biopsies and 13 cell lines. Among these were phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in de novo serine synthesis. MYCN associated with two regions in the PHGDH promoter, supporting transcriptional PHGDH regulation by MYCN. Pulsed stable isotope-resolved metabolomics utilizing 13C-glucose labeling demonstrated higher de novo serine synthesis in MYCN-amplified cells compared to cells with diploid MYCN. An independence of MYCN-amplified cells from exogenous serine and glycine was demonstrated by serine and glycine starvation, which attenuated nucleotide pools and proliferation only in cells with diploid MYCN but did not diminish these endpoints in MYCN-amplified cells. Proliferation was attenuated in MYCN-amplified cells by CRISPR/Cas9-mediated PHGDH knockout or treatment with PHGDH small molecule inhibitors without affecting cell viability. PHGDH inhibitors administered as single-agent therapy to NMRI-Foxn1nu/nu mice harboring patient-derived MYCN-amplified neuroblastoma xenografts slowed tumor growth. However, combining a PHGDH inhibitor with the standard-of-care chemotherapy drug, cisplatin, revealed antagonism of chemotherapy efficacy in vivo. Emergence of chemotherapy resistance was confirmed in the genetic PHGDH knockout model in vitro. Altogether, PHDGH knockout and inhibition by small molecules consistently slows proliferation, but stops short of killing the cells, which then establish resistance to classical chemotherapy. Although PHGDH inhibition with small molecules has produced encouraging results in other preclinical cancer models, this approach must be considered with caution in patients with neuroblastoma.